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Ammonia Synthesis Gas Compression


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#1 Said Salim

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Posted 02 January 2017 - 12:47 PM

Hello everybody,
I am in the process of evaluating an ammonia syngas compressor before and after Annual Turn round
What is the most suitable property package to simulate syngas compressor in ammonia plant?
Do you suggest any working sheet to obtain the proper evaluation.
The compressor is developing pressure from 29 Barg to 211 Barg.

#2 breizh

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Posted 02 January 2017 - 01:27 PM

Said ,

 

Why don't you refer to the data sheet supplied by the vendor ? Same they should perform acceptance tests after turn around .

 

https://books.google...epage&q&f=false

 

My 2 cents

Breizh

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Edited by breizh, 02 January 2017 - 09:15 PM.


#3 Pilesar

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Posted 03 January 2017 - 01:13 PM

Compressor vendor process modeling data is often incorrect since the machinery vendors are strong in mechanical engineering but do not often have strong chemical engineering skills. They can be very precise on the correct mechanical efficiency and still be grossly incorrect in predicting discharge temperatures. You are likely to get three different results: the vendor temperature, the process model temperature, and the actual plant temperature. Reconciling these can be difficult -- especially at such high pressures. As to property package, choose an equation of state. I suggest you compare PR and SRK in your model to see which one works the best for your situation.



#4 Pilesar

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Posted 03 January 2017 - 01:21 PM

The compressor vendor has software that simulates the inlet and outlet of each wheel. Your model will at best be per compression stage. Ideally, you can mesh both approaches into one model, but you do not have any process data for the individual wheels. Give it your best go to find the overall compressor efficiency. Get the efficiency for each stage if possible. This should be in the context of an overall synthesis loop model to reconcile with the amount of liquid condensed and the inert level.



#5 breizh

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Posted 03 January 2017 - 02:59 PM

HI Said ,

 

Let you consider the excel sheet attached , prepared a few years ago.. Hope this is going to help you .

 

Good luck .

 

Breizh

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Edited by breizh, 03 January 2017 - 03:01 PM.


#6 Saml

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Posted 04 January 2017 - 09:27 PM

My experience with a turbine driven centrifugal compressor made in Italy, on that specific service is that an equation of state (PR- SRK) works fine and matchs the vendor curves if the compressor is running well. The only exception being the synthesis loop recirculation that has a very low pressure ratio (around 1.1) making a degree C difference very significant in calculating the compressor efficiency.

 

And to detect a difference in performance before and after a turn around it will suffice



#7 Satyajit

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Posted 12 January 2017 - 06:02 PM

Hi Said,

             If your syngas is saturated with moisture, you can use Peng-Robinson property method in aspen plus to calculate each stages polytropic efficiency and also the power consumed. Compare the evaluated results with datasheet / compressor curves  supplied by compressor vendor. This will give you very clear idea how is the performance  of each stages and total power consumption by the compressor.

Kind regards,

Satyajit






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